<div class="refentry" lang="en" xml:lang="en"><a id="glBindAttribLocation"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>glBindAttribLocation — Associates a generic vertex attribute index with a named attribute variable</p></div><div class="refsynopsisdiv"><h2>C Specification</h2><div class="funcsynopsis"><table><tr><td><code class="funcdef">void <b class="fsfunc">glBindAttribLocation</b>(</code></td><td>GLuint  </td><td><var class="pdparam">program</var>, </td></tr><tr><td> </td><td>GLuint  </td><td><var class="pdparam">index</var>, </td></tr><tr><td> </td><td>const GLchar * </td><td><var class="pdparam">name</var><code>)</code>;</td></tr></table></div></div><div class="refsect1" lang="en" xml:lang="en"><a id="parameters"></a><h2>Parameters</h2><div class="variablelist"><dl><dt><span class="term"><em class="parameter"><code>program</code></em></span></dt><dd><p>Specifies the handle of the program object in
		    which the association is to be made.</p></dd><dt><span class="term"><em class="parameter"><code>index</code></em></span></dt><dd><p>Specifies the index of the generic vertex
		    attribute to be bound.</p></dd><dt><span class="term"><em class="parameter"><code>name</code></em></span></dt><dd><p>Specifies a null terminated string containing
		    the name of the vertex shader attribute variable to
		    which <em class="parameter"><code>index</code></em> is to be
		    bound.</p></dd></dl></div></div><div class="refsect1" lang="en" xml:lang="en"><a id="description"></a><h2>Description</h2><p><code class="function">glBindAttribLocation</code> is used to
	associate a user-defined attribute variable in the program
	object specified by <em class="parameter"><code>program</code></em> with a
	generic vertex attribute index. The name of the user-defined
	attribute variable is passed as a null terminated string in
	<em class="parameter"><code>name</code></em>. The generic vertex attribute index
	to be bound to this variable is specified by
	<em class="parameter"><code>index</code></em>. When
	<em class="parameter"><code>program</code></em> is made part of current state,
	values provided via the generic vertex attribute
	<em class="parameter"><code>index</code></em> will modify the value of the
	user-defined attribute variable specified by
	<em class="parameter"><code>name</code></em>.</p><p>If <em class="parameter"><code>name</code></em> refers to a matrix
	attribute variable, <em class="parameter"><code>index</code></em> refers to the
	first column of the matrix. Other matrix columns are then
	automatically bound to locations <em class="parameter"><code>index+1</code></em>
	for a matrix of type mat2; <em class="parameter"><code>index+1</code></em> and
	<em class="parameter"><code>index+2</code></em> for a matrix of type mat3; and
	<em class="parameter"><code>index+1</code></em>, <em class="parameter"><code>index+2</code></em>,
	and <em class="parameter"><code>index+3</code></em> for a matrix of type
	mat4.</p><p>This command makes it possible for vertex shaders to use
	descriptive names for attribute variables rather than generic
	variables that are numbered from 0 to
	<code class="constant">GL_MAX_VERTEX_ATTRIBS</code> -1. The values sent
	to each generic attribute index are part of current state, just
	like standard vertex attributes such as color, normal, and
	vertex position. If a different program object is made current
	by calling
	<a class="citerefentry" href="glUseProgram"><span class="citerefentry"><span class="refentrytitle">glUseProgram</span></span></a>,
	the generic vertex attributes are tracked in such a way that the
	same values will be observed by attributes in the new program
	object that are also bound to
	<em class="parameter"><code>index</code></em>.</p><p>Attribute variable
	name-to-generic attribute index bindings for a program object
	can be explicitly assigned at any time by calling
	<code class="function">glBindAttribLocation</code>. Attribute bindings do
	not go into effect until
	<a class="citerefentry" href="glLinkProgram"><span class="citerefentry"><span class="refentrytitle">glLinkProgram</span></span></a>
	is called. After a program object has been linked successfully,
	the index values for generic attributes remain fixed (and their
	values can be queried) until the next link command
	occurs.</p><p>Applications are not allowed to bind any of the standard
	OpenGL vertex attributes using this command, as they are bound
	automatically when needed. Any attribute binding that occurs
	after the program object has been linked will not take effect
	until the next time the program object is linked.</p></div><div class="refsect1" lang="en" xml:lang="en"><a id="notes"></a><h2>Notes</h2><p><code class="function">glBindAttribLocation</code> is available
	only if the GL version is 2.0 or greater.</p><p><code class="function">glBindAttribLocation</code> can be called
	before any vertex shader objects are bound to the specified
	program object. It is also permissible to bind a generic
	attribute index to an attribute variable name that is never used
	in a vertex shader.</p><p>If <em class="parameter"><code>name</code></em> was bound previously, that
	information is lost. Thus you cannot bind one user-defined
	attribute variable to multiple indices, but you can bind
	multiple user-defined attribute variables to the same
	index.</p><p>Applications are allowed to bind more than one
	user-defined attribute variable to the same generic vertex
	attribute index. This is called <span class="emphasis"><em>aliasing</em></span>,
	and it is allowed only if just one of the aliased attributes is
	active in the executable program, or if no path through the
	shader consumes more than one attribute of a set of attributes
	aliased to the same location. The compiler and linker are
	allowed to assume that no aliasing is done and are free to
	employ optimizations that work only in the absence of aliasing.
	OpenGL implementations are not required to do error checking to
	detect aliasing. Because there is no way to bind standard
	attributes, it is not possible to alias generic attributes with
	conventional ones (except for generic attribute 0).</p><p>Active attributes that are not explicitly bound will be
	bound by the linker when
	<a class="citerefentry" href="glLinkProgram"><span class="citerefentry"><span class="refentrytitle">glLinkProgram</span></span></a>
	is called. The locations assigned can be queried by calling
	<a class="citerefentry" href="glGetAttribLocation"><span class="citerefentry"><span class="refentrytitle">glGetAttribLocation</span></span></a>.</p><p>OpenGL copies the <em class="parameter"><code>name</code></em> string when
	<code class="function">glBindAttribLocation</code> is called, so an
	application may free its copy of the <em class="parameter"><code>name</code></em>
	string immediately after the function returns.</p></div><div class="refsect1" lang="en" xml:lang="en"><a id="errors"></a><h2>Errors</h2><p><code class="constant">GL_INVALID_VALUE</code> is generated if
	<em class="parameter"><code>index</code></em> is greater than or equal to
	<code class="constant">GL_MAX_VERTEX_ATTRIBS</code>.</p><p><code class="constant">GL_INVALID_OPERATION</code> is generated if
	<em class="parameter"><code>name</code></em> starts with the reserved prefix
	"gl_".</p><p><code class="constant">GL_INVALID_VALUE</code> is generated if
	<em class="parameter"><code>program</code></em> is not a value generated by
	OpenGL.</p><p><code class="constant">GL_INVALID_OPERATION</code> is generated if
	<em class="parameter"><code>program</code></em> is not a program object.</p><p><code class="constant">GL_INVALID_OPERATION</code> is generated if
	<code class="function">glBindAttribLocation</code> is executed between
	the execution of
	<a class="citerefentry" href="glBegin"><span class="citerefentry"><span class="refentrytitle">glBegin</span></span></a>
	and the corresponding execution of
	<a class="citerefentry" href="glEnd"><span class="citerefentry"><span class="refentrytitle">glEnd</span></span></a>.</p></div><div class="refsect1" lang="en" xml:lang="en"><a id="associatedgets"></a><h2>Associated Gets</h2><p><a class="citerefentry" href="glGet"><span class="citerefentry"><span class="refentrytitle">glGet</span></span></a>
	with argument <code class="constant">GL_MAX_VERTEX_ATTRIBS</code></p><p><a class="citerefentry" href="glGetActiveAttrib"><span class="citerefentry"><span class="refentrytitle">glGetActiveAttrib</span></span></a>
	with argument <em class="parameter"><code>program</code></em></p><p><a class="citerefentry" href="glGetAttribLocation"><span class="citerefentry"><span class="refentrytitle">glGetAttribLocation</span></span></a>
	with arguments <em class="parameter"><code>program</code></em> and
	<em class="parameter"><code>name</code></em></p><p><a class="citerefentry" href="glIsProgram"><span class="citerefentry"><span class="refentrytitle">glIsProgram</span></span></a></p></div>
        {$pipelinestall}{$examples}
        <div class="refsect1" lang="en" xml:lang="en"><a id="seealso"></a><h2>See Also</h2><p><a class="citerefentry" href="glDisableVertexAttribArray"><span class="citerefentry"><span class="refentrytitle">glDisableVertexAttribArray</span></span></a>,
	<a class="citerefentry" href="glEnableVertexAttribArray"><span class="citerefentry"><span class="refentrytitle">glEnableVertexAttribArray</span></span></a>,
	<a class="citerefentry" href="glUseProgram"><span class="citerefentry"><span class="refentrytitle">glUseProgram</span></span></a>,
	<a class="citerefentry" href="glVertexAttrib"><span class="citerefentry"><span class="refentrytitle">glVertexAttrib</span></span></a>,
	<a class="citerefentry" href="glVertexAttribPointer"><span class="citerefentry"><span class="refentrytitle">glVertexAttribPointer</span></span></a></p></div><div class="refsect1" lang="en" xml:lang="en"><div id="Copyright"><h2>Copyright</h2><p>
            Copyright © 2003-2005 3Dlabs Inc. Ltd.
            This material may be distributed subject to the terms and conditions set forth in
            the Open Publication License, v 1.0, 8 June 1999.
            <a class="ulink" href="http://opencontent.org/openpub/" target="_top">http://opencontent.org/openpub/</a>.
        </p></div></div></div>
